Various types of seed meters have been developed that use an air pressure differential, either vacuum or positive pressure, to adhere seed to a metering member. The metering member takes seed from a seed pool and sequentially discharges single seeds. (In some cases, multiple seeds may be discharged at a time.) One common type of seed meter is shown in U.S. Pat. No. 5,170,909. There, a seed disk 48 contained in a housing is used to meter the seed. The seed pool is positioned on one side of the disk at a lower portion thereof while vacuum is applied to the opposite side of the disk. As the disk is rotated, individual seeds from the seed pool are adhered by the vacuum to apertures that extend though the disk. When the seed reaches a desired release position, the vacuum is terminated, allowing the seed to drop from the disk, through a seed tube to a furrow formed in the soil below.
Flexible belts have also been used in an air pressure differential seed meter. One example is shown in US patent application 2010/0192818 A1. There, a flexible belt having an array of apertures therein is movable along a path in a housing. A seed pool is formed on one side of the belt. Vacuum applied on the opposite side of the belt along a portion of the belt path adheres seed to the apertures, allowing the belt to move the seed to a release position where the vacuum is cut-off. The seed then falls or is removed from the belt.
When seed falls by gravity from the meter through the seed tube, it can be difficult to maintain accurate and consistent seed spacing at planting speeds greater than about 8 kph (5 mph). To maintain spacing accuracy, a seed delivery system that controls the seed as the seed moves from the seed meter to the soil is desirable. One such delivery system is shown in US patent application 2010/0192819-A1. With such a delivery system, the hand-off of seed from the disk of U.S. Pat. No. 5,170,909 to the delivery system is difficult to achieve In a consistent manner. While the hand-off of seed may be improved with the use of a belt meter, there is still a need for a more consistent and reliable hand-off of seed from the seed meter to the delivery system.